1. Field of the Invention
The invention relates to an ultrasound sensor for a fumes extractor hood with automatic compensation in respect of temperature and ageing drift, wherein the ultrasound sensor comprising a transmitter and a receiver monitors the vapour rising from the cooking to the fumes extractor hood and wherein the ultrasound sensor has a system-specific resonance frequency.
2. Discussion of the Prior Art
It is known from EP 0 443 141 B1 to use ultrasound sensors for controlling the fan in fumes extractor hoods. That involves taking advantage of the realisation that the rising vapours alter the amplitude of the ultrasound signal, more specifically, the amplitude of the ultrasound signal being altered to an increasing degree in proportion to increasing vapour formation. It is known in relation to ultrasound sensors for temperature drift to be automatically compensated, but hitherto there were no indications as to how the ageing drift of the sensor is compensated during on-going operation of the ultrasound sensor. Ageing drift results in a change in the resonance frequency of the sensor and therefore has to be monitored. Hitherto the necessary compensation effect is possible only in regard to a calm-air signal section and hitherto a strict association between sensor and associated electronics was also necessary as generally compensation could not be effected in the installed condition.